COULTER HmX Hematology Analyzer, Reference Manual

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PN 4237523A 3-11
OPERATION PRINCIPLES
COUNTING AND SIZING
3
Sweep Flow
The sweep flow is a steady stream of diluent that flows behind the RBC aperture during the
sensing periods (B). This keeps cells from swirling back into the sensing zone. Because these
swirling cells (A) would be peripherally sensed, their pulse height would be similar to Plt
pulse heights. See Figure 3.11.
Figure 3.11 Sweep Flow
Pulse Editing
When cells pass through the aperture near the edge or at an angle rather than at the center,
they create atypical pulses. Pulse editing technology eliminates atypical pulses from the
analysis because they distort the true size of the cell. This prevents atypical pulses from
influencing size measurements.
RBC Count and Size Distribution
During RBC sensing, pulses that represent cells from 36 fL to 360 fL are classified as RBCs
and are sorted by size into 256 channels to build the RBC histogram. Using a system of
moving averages, the computer smooths the histogram curve.
Plt Count and Size Distribution
During RBC sensing, pulses that represent cells from 2 to 20 fL are classified as platelets. The
system automatically extends the sensing time if platelet accumulation is below a
predetermined level. The system sorts the Plt pulses by size into 64 channels to build the Plt
histogram.
Sensing
zone
Swirling
effect
No
sweep
flow
A B
Cell
Sweep
flow
Cell
Sensing
zone
To
waste